Problem: Add. $\dfrac{2}{3} + \dfrac{9}{12} = $
Solution: ${\dfrac{2}{3}}$ ${\dfrac{9}{12}}$ $+$ ${\dfrac{2 \times 4}{3 \times 4}}$ ${\dfrac{9 \times 1}{12 \times 1}}$ $+$ ${\dfrac{8}{12}}$ ${\dfrac{9}{12}}$ $+$ $ = \dfrac{{8} + {9}}{12} $ $ = \dfrac{17}{12}$